Exported variable in bashrc file not visible when running as another user-CodePudding

On Ubuntu 20.04LTS:

Create a dummy user.
Create a short script that appends an exported variable to the new user's .bashrc, then sources that .bashrc and tries to use the variable.
Run the script as the new user.

Why is the variable not set?

> adduser --gecos ',,,' --disabled-password foouser
[...output...]
> cat > /tmp/bootstrap.sh <<EOF
  echo 'export FOO=foo' >> /home/foouser/.bashrc
  . /home/foouser/.bashrc
  echo 'sourced foouser bashrc'
  set | grep FOO
EOF
> chmod a x /tmp/bootstrap.sh
> su - foouser -c /tmp/bootstrap.sh
[...output does not include FOO...]
> deluser --remove-home foouser

CodePudding user response：

Your problem is that .bashrc is configure explicitly to only run for interactive shells. Look at the top of /home/foouser/.bashrc:

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;
esac

If you add a set -x to your /tmp/bootstrap.sh script, you will see when you execute it the following:

  echo 'export FOO=foo'
  . /home/foouser/.bashrc
   case $- in
   return
  echo 'sourced foouser bashrc'
sourced foouser bashrc
  set
  grep FOO

There you can see it hits the return command in the case statement.

You can force an interactive shell with the -i option:

root@ed3085a447ad:/# su - foouser -c 'bash -i -c /tmp/bootstrap.sh'
bash: cannot set terminal process group (-1): Inappropriate ioctl for device
bash: no job control in this shell
sourced foouser bashrc
FOO=foo